A wearable walking-guide system for the blind is developed in Korea. It is designed to find out the obstacles in front of the user using ultrasound sensors and notify the information of it using bone conduction vibrator with beep sound and TTS voice announcement. A PDA is used as a main controller and provides the warning and guide information sound to the blind and voice recognition method is employed for the user convenience. As the information transfer method, the bone conduction method is applied in order to hear for the blind both the guide sound and the environmental sound which the blind use as one of essential cue for walking. Considering the blind’s inclination of covering their disability, we designed the wearable type system. Therefore, almost of the system is concealed in the clothes and we expect that the blind will use this system without any hesitation.
guide system, the blind, bone conduction, wearable system
There are over than 180 thousands visually impaired or blind persons in Korea and the number of these people is growing every year [(1)]. Although there are some differences, almost of the blind have serious trouble to go to somewhere and most of them use the white cane as an assistive device for walking. And some of the blind rely on the Guide Dog or other assistant. But these assistive methods have some problems and cannot be solution about the handicap. Recently, new assistive devices for walking are introduced such as electronic travel aids (ETAs), laser cane, Mowat sensor, mobile robot, etc [(2)-(5)]. Although many benefits from the devices, most of the Korean blind persons do not know about it or they are afraid of using the new devices. The important reason of that is price, performance, inconvenience, discordance in Korean environment, and so on. However, we think, the main reason of that is adaptation about the new equipment. Most of the blind are accustomed to using of white cane for walking and they don’t try to use any other new assistive device. In addition, most special school in Korea teaches and encourages only the use of white cane. Therefore, we have investigated convenient and easily accustomed guide system for the blind. We designed a vest type of wearable guide system in which all the components of system located as shown in Fig. 1. Only putting on the vest, the user can acquire the information about obstacles and direction for walking and they can use white cane together if they want. Moreover, this system is concealed in the clothes and it may reduce a sense of shame about bringing their disability before the public.
In this system, six ultrasonic sensors (UM2, DAS Co.) are used for detecting the obstacles in front of the user. Ultra sensors are located at the front part of vest. The detecting range and angle using ultrasonic sensors are 0.4-2 m, 150˚ (azimuth) and 60˚ (elevation). To calculate the position of obstacles, TOF (time of flight) and ITD (inter-aural time difference) method are used. The front direction of the user is divided into five sections as shown in Fig. 2 and the section in which obstacle locate is notified to the user.
As a user interface, the voice recognition method and the stereo bone conduction method is employed. Therefore, the user can drive the system only speech the assigned sound order and the warning and guide sound are transmitted to the user by bone conduction vibrator which located at the behind ear. Therefore, ear canal of user is vacant because he/she don’t use earphone and he/she can hear the environmental sound well not interfered by guide sound.
The stereo bone stimulation is employed for indicating the direction of obstacle. We designed that the bone vibrator of obstacle’s direction generate more loud beep sound and the user become aware of the obstacle’s direction only compare the left and right sound intensity. To indicate the distance from the obstacle, the frequency of the beep sound is modulated. If the distance is lower than 1 meter, 1 kHz beep sound is generated and over than 1 meter, 500Hz sound is transmitted. And we designed that the sound interval is different from the height of the obstacle. If the obstacle is located over 1 meter height, vibrator has 0.5 second sound interval and 0.25 second sound interval against under 1 meter height. For more exact guide, the direction of obstacle is notified to the user by voice sound using text-to-speech (TTS) program concurrently.
The designed prototype walking guide system was implemented and obstacle detecting experiment was carried out as shown in Fig. 3. The implemented system had 3 meter detection distance and 180 degree (azimuth) and 70 degree (elevation) of detecting angle. It could find out 15cm size of object at 1 meter distance. And it had 250mA current consumption using 12V rechargeable battery.
We are going to employ the GPS to this system in near future. After that it will be more useful and handy device for the blind. We don’t carry out the road test using the prototype system yet. We think it is not perfectly suitable in Korean road environment. More investigation and progress is required and strict field test and feedback should be requested. But, after all, we expect that the blind can walk around with safety and convenience using the newly designed wearable guide system.
This study was supported by a grant of the Korea Health 21 R&D Project, Ministry of Health & Welfare, Republic of Korea. (02-PJ3-PG6-EV10-0001) and this work was supported by the Brain Korea 21 Project in 2007.
Byung-Seop Song, Ph.D.
School of Rehabilitation Science, Daegu University
2288 Daemyung-Dong Namgu Daegu, 705-714, Korea
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